Continuous production of fuel grade hydrocarbons by hydrotreatment of forestry byproduct lignin

ABSTRACT

The present invention relates to a composition and a method of preparing the composition where the composition comprises lignin dissolved in depolymerized lignin obtained from hydrotreatment of lignin. The method may be operated in batch mode or in a continuous mode but there is no need to add any oil.

FIELD OF THE INVENTION

The present invention relates to a composition and a method of preparingthe composition where the composition comprises lignin dissolved inlignin derived hydrotreated compounds. The method may be operated inbatch mode or in a continuous mode but there is no need to add anymineral oil.

BACKGROUND

There is an increasing interest in using biomass as a source for fuelproduction. Biomass includes, but is not limited to, plant parts,fruits, vegetables, processing waste, wood chips, chaff, grain, grasses,com, com husks, weeds, aquatic plants, hay, paper, paper products,recycled paper and paper products, lignocellulosic material, lignin andany cellulose containing biological material or material of biologicalorigin.

An important component of biomass is the lignin present in the solidportions of the biomass. Lignin comprises chains of aromatic andoxygenate constituents forming larger molecules that are not easilytreated. A major reason for the difficulty in treating the lignin is theinability to disperse or dissolve the lignin for contact with catalyststhat can break down the lignin.

Lignin is one of the most abundant natural polymers on earth. One commonway of preparing lignin is by separation from wood during pulpingprocesses. Only a small amount (1-2%) is utilized in specialty productswhereas the rest primary serves as fuel. Even if burning lignin is avaluable way to reduce usage of fossil fuel, lignin has significantpotential as raw material for the sustainable production of chemicalsand liquid fuels.

Various lignins differ structurally depending on raw material source andsubsequent processing, but one common feature is a backbone consistingof various substituted phenyl propane units that are bound to each othervia aryl ether or carbon-carbon linkages. They are typically substitutedwith methoxyl groups and the phenolic and aliphatic hydroxyl groupsprovide sites for e.g. further functionalization.

Today lignin may be used as a component in for example pellet fuel as abinder but it may also be used as an energy source due to its highenergy content. Lignin has higher energy content than cellulose orhemicelluloses and one gram of lignin has on average 22.7 KJ, which is30% more than the energy content of cellulosic carbohydrate. The energycontent of lignin is similar to that of coal. Today, due to its fuelvalue lignin that has been removed using the kraft process, sulphateprocess, in a pulp or paper mill, is usually burned in order to provideenergy to run the production process and to recover the chemicals fromthe cooking liquor.

There are several ways of separating lignin from black or red liquorobtained after separating the cellulose fibres in the kraft or sulphiteprocess respectively, during the production processes. One of the mostcommon strategies is ultra-filtration. Lignoboost® is a separationprocess developed by Innventia AB and the process has been shown toincrease the lignin yield using less sulphuric acid. In the Lignoboost®process, black liquor from the production processes is taken and thelignin is precipitated through the addition and reaction with acid,usually carbon dioxide (CO₂), and the lignin is then filtered off. Thelignin filter cake is then re-dispersed and acidified, usually usingsulphuric acid, and the obtained slurry is then filtered and washedusing displacement washing. The lignin is usually then dried andpulverized in order to make it suitable for lime kiln burners or beforepelletizing it into pellet fuel.

Biofuel, such as biogasoline and biodiesel, is a fuel in which theenergy is mainly derived from biomass material or gases such as wood,corn, sugarcane, animal fat, vegetable oils and so on. However thebiofuel industries are struggling with issues like food vs fuel debate,efficiency and the general supply of raw material. At the same time thepulp or paper making industries produces huge amounts of lignin which isoften, as described above, only burned in the mill. Two commonstrategies for exploring biomass as a fuel or fuel component are to usepyrolysis oils or hydrogenated lignin.

In order to make lignin more useful as a source for fuel production onehas to solve the problem with the low solubility of lignin in organicsolvents. One drawback of using lignin as a source for fuel productionis the issue of providing lignin in a form suitable for hydrotreaters orcrackers. The problem is that lignin is not soluble in oils or fattyacids which is, if not necessary, highly wanted.

Prior art provides various strategies for degrading lignin into smallunits or molecules in order to prepare lignin derivatives that may beprocessed. These strategies include hydrogenation, dexoygenation andacid catalyst cleaving. WO2011003029 relates to a method for catalyticcleavage of carbon-carbon bonds and carbon-oxygen bonds in lignin.US20130025191 relates to a depolymerisation and deoxygenation methodwhere lignin is treated with hydrogen together with a catalyst in anaromatic solvent. All these strategies relates to methods where thedegradation is performed prior to eventual mixing in fatty acids or gasoils. WO2008157164 discloses an alternative strategy where a firstdispersion agent is used to form a biomass suspension to obtain a bettercontact with the catalyst. These strategies usually also requiresisolation of the degradation products in order to separate them fromunwanted reagents such as solvents or catalysts.

The direct treatment of lignin at present day refineries has not yetbeen realized. This has mainly to do with compatibility issues as thephysical properties of lignin are very different as compared to thestandard refinery oil feeds.

Producing pyrolysis oils or synthesis gas from biomass is howeverpossible and has been done both in Sweden and elsewhere. The productioncan be via pyrolysis of black liquor or biomass in an oil based slurry.However, refineries cannot handle the corrosive pyrolysis oils and thesyngas products methanol, which is poisonous, and dimethyl ether (DME),which is gaseous, cannot be used in currents automobile engines.

A variety of fats and greases derived from biomass have already foundtheir way into everyday fuels (Hydrogenated vegetable oil (HVO)). Someof the companies that actively use these raw materials are Preem(Evolution Diesel®), Neste (NexBTL®), and ENI (Ecofining™ process). Theuse of tall oil is not controversial as it is a forestry byproduct. Usepalm oil in the production of “green” fuels has received unwantedattention from Green Peace because palm oil is associated with thedestruction of the rainforests. ENI uses first generation vegetable oilsin their production of green fuels, however, their feedstock productionclashes with the production of food.

When focusing on the lignin part of biomass there are several differentstrategies for producing liquid fuels. One of the main strategies tomake a feedstock for oil refineries is to perform lignindepolymerization. However, many of the monomeric lignin units generatedin this way are not soluble in standard refinery carrier oils, as shownin WO2014116173. An alternative strategy is through ligninhydrotreatment. Much of the research into lignin hydrotreating has beenfocused on lignin model compounds. The few reports where actual ligninis used show that lignin can be hydrotreated in the presence ofconventional catalysts in a batch setup under solvent-free conditions orwith solvent. Solvent-free conditions may be problematic to use forcontinuous industrial hydrotreatment as the lignin powder would need tobe transported into a reactor at high gas pressures. However, usingmethanol, a report shows that “under optimal reaction conditions, themain products are alkylphenolics and gratifyingly no ring hydrogenationor char formation takes place”.

Today only the HVO is believed to have successfully been commercializedas fuel. The feedstock limitations (tall oil) or the detrimentalenvironmental effects (palm oil) will continue to be issues for theproduction of green fuels from biomass oils. There is a need to findreliable, economical ways to use renewable biomass to produce liquidfuels. One such way has been developed by RenFuel AB. They convertlignin into a lignin oil, Lignol® which is soluble in gas oils forexample used for hydrotreating.

An alternative procedure for making liquid fuels is by performinghydrotreatment of solid lignin dispersed in hydrocarbon oil. U.S. Pat.No. 7,994,375 discloses a method of converting biomass such as lignininto liquid fuel. The method comprises forming a slurry of lignin and acarrier oil (Tall oil for example) which is hydrotreated into diesel ornaphtha boiling range products. The disclosed process aims at fullydeoxygenate the lignin. There are however some obvious issues withhaving a slurry, including sedimentation, pumping problems and loss inreactivity. Also the catalyst activity may be hampered by the largeslurry particles. Using hydrotreated pyrolysis oil as a carrier liquidcomes with the problem of corrosion since pyrolysis oils have a pH of2-3 which may result in release of metals which in turn damage thecatalysts.

GB2104545 discloses a process where a slurry of lignin is treated in ahydrocracking reactor. The process results in an oil (slurrying oil)which is mixed with the lignin to prepare a pumpable slurry mixture. Theslurry mixture is then introduced into a cracking reactor where thecatalyst is provided in particulate form. A problem with using a slurryis that a fixed bed catalyst cannot be used and it is only the lignin insolution that is hydrotread i.e. the particulate lignin is not or onlypoorly hydrotreated.

Some of the problems associated with the hydrotreatment of lignin whichneed solving to become industrially interesting are:

-   -   Lignin does not significantly dissolve in carrier liquids    -   Expensive to use standard solvents as carrier liquids, i.e.        methanol    -   Using vegetable oils is too often associated with either        destruction of rainforest to produce palm oil or competition        with food to produce vegetable oils.

SUMMARY OF THE INVENTION

The aim of the present invention is to overcome the drawbacks of theprior art and provide a composition comprising lignin and depolymerized.The present invention further aims at presenting a novel method ofpreparing green light products. One application for the composition maybe as a raw material for fuel production (e.g. petrol or diesel) or asan additive to fuel or oil or as a starting material for the chemicalindustry.

Enabling the use of a fixed bed reactor will solve many issues as thelignin will contain relatively high amounts of metals, as compared to adistilled mineral oil, the reactor might need a guard bed. As aconsequence of the high oxygen content in lignin the fixed bed reactorcan handle the exothermic reaction of water formation by having lowactivity on the first bed followed by beds with more active catalyst. Inaddition the fully dissolved lignin enables the use of lower temperatureand lower hydrogen pressure as compare to having the lignin in a slurry.Furthermore by dissolving the lignin in a carrier liquid or in suitablesolvents commercially available and standard hydrotreater reactors andsystem may be used to treat the lignin instead of specifically designedhydrotreaters.

In a first aspect the present invention relates to composition asdefined in claim 1.

In a second aspect the present invention relates to method of preparingthe composition according to the present invention wherein the methodcomprises:

-   -   a. providing a first feed of lignin wherein the feed is a        liquid;    -   b. hydrotreating the lignin forming a first product stream        comprising light compounds and depolymerized lignin;    -   c. removing the light compounds from the first product stream        leaving a second product stream comprising depolymerized lignin;    -   d. providing a second feed of lignin; and    -   e. mixing the second product stream with the second feed of        lignin.

In a third aspect the present invention relates to an intermediatecomposition comprising lignin at least partly dissolved or dissolved indepolymerized lignin such as a mixture comprising phenol derivatives andpolyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol oran alkoxyphenol and a diphenol.

In a fourth aspect the present invention relates to a fuel obtained bythe method according to the present invention.

All the embodiments described herein are applicable to all the aspectsunless stated otherwise.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1, a schematic disclosure of the Bergius process

FIG. 2, the effect on polarity during hydrotreatment.

FIG. 3, a schematic overview of the present invention. The compoundsthat are found at the upper part of the column are smaller and containless oxygen than compounds further down the column.

FIG. 4, a schematic disclosure of the effect of hydrotreating ondifferent materials of the feed.

FIG. 5, HSQC comparison between the Lignoboost® starting material andthe hydrotreated product.

FIG. 6, HSQC NMR-spectrum of lignin dissolved in guaiacol which has beenhydrotreated.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a composition for use in a refineryprocesses for the production of various fuels or chemicals.

In the present application the term “lignin” means a polymer comprisingcoumaryl alcohol, coniferyl alcohol and sinapyl alcohol monomers.

In the present application the term “carrier liquid” means a liquidselected from fatty acids or mixture of fatty acids, esterified fattyacids, rosin acid, crude oil, mineral oil, bunker fuel and hydrocarbonoils or mixtures thereof.

In the present invention the term “oil” means a nonpolar chemicalsubstance that is a viscous liquid at ambient temperature and is bothhydrophobic and lipophilic.

In the present application the terms “red liquor” and “brown liquor”denote the same liquor.

In the present invention the term “hydrogen donor” should be interpretedas a substance or compound that gives or transfers hydrogen atoms toanother substance or compound.

For the purpose of this application the term “membrane filtration” shallinclude both cross-flow and dead-end flow modes by the use of porousmembranes or filters.

In the present application the terms “heavy products” and “depolymerizedlignin” denotes the same thing and are used interchangeably.

In the present application the terms “green carrier liquid” and “greencarrier oil” denotes the same thing and are used interchangeably.

Oil refineries cannot use lignin as feedstock in current hydrotreatersas lignin does not dissolve in standard carrier oil. In the Bergiusprocess coal is finely divided and formulated in recirculated heavy oiland then treated under hydrogen in presence of a solid catalyst atelevated temperatures. In the hydrotreatment process heavy oils, middleoils, gasoline, and gases are generated. After fractionation throughdistillation the gases, gasoline, and middle oils continue to becomeproducts of various kinds while the heavy oils are recirculated forreuse as carrier oil for more coal (FIG. 1). Instead the presentinvention relates to formulate lignin in depolymerized lignin orrecirculated partially hydrotreated lignin which will serve as carrierliquid for a hydrotreater replacing the gas oil (FIG. 3). Thedepolymerized lignin may be prepared by hydrotreatment, hydrothermaltreatment, hydrothermal cracking or solvolysis or any combinationthereof.

There are two different processes in the hydrotreatment which areintimately related as they both involve the cleavage of C—O bonds;depolymerization and hydrophobization. The depolymerization is mostly aconsequence of ether bond cleavages while hydrophobization is associatedwith the removal of hydroxyl-groups. The starting material lignin ispolar, while completely deoxygenated compounds, i.e. pure hydrocarbonsare non-polar. The polarity of the feed changes as it goes through thehydrotreater and becomes less polar (FIG. 2). The feed also becomessmaller through the process of depolymerization.

One object of the present invention is to develop a new method to enablethe formulation of lignin into green carrier oils or liquids which canbe pumped into conventional hydrotreaters for conversion into greenlight products. The green carrier oil is produced by the partialdeoxygenation of lignin through hydrotreatment or by hydrothermaltreatment or hydrothermal cracking or solvolysis or any combinationthereof.

Unlike U.S. Pat. No. 7,994,375 the present invention is not dependent onfurther addition of a carrier liquid and solves another problem which isto form a solution of lignin where the lignin is dissolved inhydrotreated lignin compounds. The present invention does not aim atfully deoxygenate the lignin only to the extent that it dissolveslignin.

The method according to the present invention may be a continuousprocess or a batch process.

Lignin

In order to obtain lignin biomass may be treated in any suitable wayknown to a person skilled in the art. The biomass may be treated withpulping processes or organosols processes for example. Biomass includes,but is not limited to wood, fruits, vegetables, processing waste, chaff,grain, grasses, com, com husks, weeds, aquatic plants, hay, paper, paperproducts, recycled paper, shell, brown coal, algae, straw, bark or nutshells, lignocellulosic material, lignin and any cellulose containingbiological material or material of biological origin. In one embodimentthe biomass is wood, preferably particulate wood such as saw dust orwood chips. The wood may be any kind of wood, hard or soft wood,coniferous tree or broad-leaf tree. A non-limiting list of woods wouldbe pine, birch, spruce, maple, ash, mountain ash, redwood, alder, elm,oak, larch, yew, chestnut, olive, cypress, banyan, sycamore, cherry,apple, pear, hawthorn, magnolia, sequoia, walnut, karri, coolabah andbeech.

It is preferred that the biomass contains as much lignin as possible.The Kappa number estimates the amount of chemicals required duringbleaching of wood pulp in order to obtain a pulp with a given degree ofwhiteness. Since the amount of bleach needed is related to the lignincontent of the pulp, the Kappa number can be used to monitor theeffectiveness of the lignin-extraction phase of the pulping process. Itis approximately proportional to the residual lignin content of thepulp.

K≈c*1

K: Kappa number; c: constant 6.57 (dependent on process and wood); l:lignin content in percent. The Kappa number is determined by ISO302:2004. The kappa number may be 20 or higher, or 40 or higher, or 60or higher. In one embodiment the kappa number is 10-100.

The biomass material may be a mixture of biomass materials and in oneembodiment the biomass material is black or red liquor, or materialsobtained from black or red liquor. Black and red liquor containscellulose, hemi cellulose and lignin and derivatives thereof and cookingchemicals. The composition according to the present invention maycomprise black or red liquor, or lignin obtained from black or redliquor.

Black liquor comprises four main groups of organic substances, around30-45 weight % ligneous material, 25-35 weight % saccharine acids, about10 weight % formic and acetic acid, 3-5 weight % extractives, about 1weight % methanol, and many inorganic elements and sulphur. The exactcomposition of the liquor varies and depends on the cooking conditionsin the production process and the feedstock. Red liquor comprises theions from the sulfite process (calcium, sodium, magnesium or ammonium),sulfonated lignin, hemicellulose and low molecular resins.

The lignin according to the present invention may be Kraft lignin,sulfonated lignin, Lignoboost® lignin, precipitated lignin, filtratedlignin, acetosolv lignin or organosolv lignin. In one embodiment thelignin is Kraft lignin, acetosolv lignin or organosolv lignin. Inanother embodiment the lignin is Kraft lignin. In another embodiment thelignin is organosolv lignin. In another embodiment the lignin obtainedas residual material from ethanol production. The lignin may when addedb in particulate form with a particle size of 5 mm or less, or 1 mm orless, or 500 μm or less, or 300 μm or less.

A problem with lignin, native lignin or Kraft lignin for example, isthat it is not soluble in most organic solvents, fatty acids or oils.Instead prior art have presented various techniques to depolymerize andcovert the depolymerized lignin into components soluble in the wantedmedia.

One of the mildest ways of attaining lignin from wood is by organosolvpulping. Through this method the lignin retains much of its nativestructure with many ether bonds. This makes organosolv lignin easy todepolymerize and deoxygenate. Unlike organosolv lignin Kraft lignin isharshly processed in order to remove much lignin from the cellulosefibres in the Kraft process. Through the Kraft process the native ligninis destroyed and recondensed into Kraft lignin which is very resilienttowards chemical treatment. The chemical bonds in Kraft lignin are moredifficult to cleave as compared to organosolv lignin. Reviewing therecent literature on lignin catalysis much of the work is focused onorganosolv lignin as this lignin is much more effected by catalysis ascompared to Kraft lignin. Even if the use of organosolv lignin inhydrotreating is easier there is much more Kraft lignin available thanorganosolv lignin making Kraft lignin a more interesting source.

The weight average molecular weight (mass) (M_(w)) of the ligninaccording to the present invention may be 30,000 g/mol or less, such asnot more than 20,000 g/mol, or not more than 10,000 g/mol, or not morethan 5,000 g/mol, or not more than 2,000 g/mol, but preferably higherthan 1,000 g/mol, or higher than 1,200 g/mol, or higher than 1,500g/mol. In one embodiment the number average molecular weight of thelignin is between 1000 and 4,000 g/mol, or between 1,500 and 3,500g/mol. Kraft lignin usually have a molecular weight (Mw) of around2,000-10,000 g/mol such as 2,500 and 5,000 depending on the Kraftprocess conditions.

The amount of lignin, non-hydrotreated lignin, in the composition may be1-50 wt % such as 2 wt % or more, or 3 wt % or more, or 5 wt % or more,or 10 wt % or more, but 40 wt % or less, or 30 wt % or less, or 20 wt %or less, or 15 wt % or less. Lower amounts of lignin makes thecomposition more easy to pump and to high amounts of lignin may make thehydrotreatment less efficient. The composition may also comprisehydrotreated lignin obtained from the hydrotreatment of a previous oranother composition according to the invention.

The composition is preferably free or essentially free of particleswhich may block or interfere with the catalyst in the hydrotreater whichwould reduce the flow through and the efficiency of the hydrotreater.The composition may in one embodiment be defined as not being a slurry.In one embodiment the composition is free of particles having a diameterof 5 mm or more, or 3 mm or more, or 1 mm or more, or 500 μm or more, or300 μm or more, or 100 μm or more, or 50 μm or more, or 20 μm or more.

Method of Treating Lignin

The method according to the present invention aims at preparing lightcompounds that may be used as fuel components or additives to fuels orcompounds that may be further refined in a hydrotreater or a catalyticcracker for example. The method is schematically disclosed in FIG. 3 andcomprises providing a first feed of lignin where the feed is a liquid ora solution. The feed may be lignin dissolved in a solvent or for exampleblack liquor. The first feed may comprise depolymerized lignin, anorganic solvent or a mixture of organic solvents or a mixture ofdepolymerized lignin and at least one organic solvent. The first feedmay be prepared at a temperature of at least 50° C. or higher, or 70° C.or higher, or 90° C. or higher.

The first feed comprising a solution of lignin is introduced into ahydrotreater where the feed is hydrotreated using any suitablehydrotreating technique forming a first product stream comprising lightcompounds and depolymerized lignin (heavy compounds). The ratio of lightcompounds and depolymerized lignin depends on the hydrotreatingconditions such as time, temperature, pressure, catalyst and hydrogendonor. From the first product stream the light compounds are removed(denoted “Gasoline” and “Diesel” in FIG. 3), for example by distillationor evaporation, and leaves a second product stream (denoted “greencarrier liquid” in FIG. 3) comprising the depolymerized lignin. Thelight compounds may be further treated using an additional hydrotreateror a catalytic cracker for example. A second feed of lignin is thenprovided and mixed with the second product stream or the depolymerizedlignin. The depolymerized lignin at least partly dissolve or fullydissolve the lignin of the second feed making the lignin moresusceptible to hydrotreatment making the hydrotreatment more efficient.The second feed of lignin may be prepared as the first feed of ligninand may comprise the same solvent or mixture of solvents as the firstfeed of lignin. This is of course also true for every subsequent feed oflignin.

The feed of lignin entering the hydrotreated is preferably a fullydissolved solution. The feed is also preferably essentially free fromparticles. FIG. 3 discloses a schematic view of the method and thecompounds and temperatures disclosed in the figure are only examples andshould not be seen as limiting. The method may be adapted by the skilledperson in order to prepare a first and a second and a subsequent productstream which contains the wanted compounds.

Performing hydrotreating over a series of packed beds instead of in aslurry gives much greater possibilities to control the hydrotreatingprocess. Different catalytic materials can be placed in differentpositions in the beds to give optimal performance. The hydrogen flow andtemperature can be optimized for each bed to give the optimal degree ofhydrotreating and product properties.

The hydrotreater used in the present invention may be a fixed bedhydrotreater. The hydrotreater reactor may comprise one or more fixedbeds where each bed may contain different catalysts. The system may alsocontain a guard bed arranged prior to or inside the reactor in order toremove metals and optionally also a particle filter arranged at theinlet or prior to the inlet of the hydrotreater.

The mixing of the second product stream and the second feed of ligninmay be done at a temperature of at least 50° C. or higher, or 70° C. orhigher, or 90° C. or higher. The mixing may be done using stirring orshaking or any other suitable method. The mixing may be an extractionstep where the second product stream extracts lignin from a liquidlignin composition such as black liquor.

This method may be operated continuously, in other words a more or lesscontinuous second feed of lignin (dry or in liquid phase) may be mixedas described herein with the continuously prepared second product streamof depolymerized lignin. The second product stream may vary for eachcycle and may comprise different compounds or may comprise differentratios of the compounds for each cycle.

The addition of the hydrogen gas or hydrogen donor (H-donor) may be donein the hydrotreater or prior to feeding the lignin or lignin containingmixture into the hydrotreater.

The present invention provides a method of preparing light compoundsfrom lignin without the need to add fossil fuels or oils, or the use offatty acids derived from crops. By hydrotreating lignin the methodprepares a solvent for dissolving lignin. The present invention is alsobelieved to result in high yield of high valuable products and low cokeformation. By adjusting the parameters of the method such astemperature, time, pressure and catalyst the present method may beadapted to obtain specific products from the hydrotreatment step so thatthe first product stream contains the wanted products and the secondproduct stream contains compounds that dissolve lignin.

Hydrotreating and Cracking

Hydrotreating and catalytic cracking are common steps in the oilrefinery process where the sulfur, oxygen and nitrogen contents of theoil is reduced and where high-boiling, high molecular weighthydrocarbons are converted into gasoline, diesel and gases. Duringhydrotreating the feed is normally exposed to hydrogen gas (for example20-200 bar) and a hydrotreating catalyst (NiMo, CoMo or other HDS, HDN,HDO catalyst) at elevated temperatures (200-500° C.). The hydrotreatmentprocess results in hydrodesulfurization (HDS), hydrodenitrogenation(HDN), and hydrodeoxygenation (HDO) where the sulphurs, nitrogens andoxygens primarily are removed as hydrogen sulfide, ammonia, and water.Hydrotreatment also results in the saturation of olefins. Catalyticcracking is a category of the broader refinery process of cracking.During cracking, large molecules are split into smaller molecules underthe influence of heat, catalyst, and/or solvent. There are severalsub-categories of cracking which includes thermal cracking, steamcracking, fluid catalyst cracking and hydrocracking. During thermalcracking the feed is exposed to high temperatures and mainly results inhomolytic bond cleavage to produce smaller unsaturated molecules. Steamcracking is a version of thermal cracking where the feed is diluted withsteam before being exposed to the high temperature at which crackingoccurs. In a fluidized catalytic cracker (FCC) or “cat cracker” thepreheated feed is mixed with a hot catalyst and is allowed to react atelevated temperature. The main purpose of the FCC unit is to producegasoline range hydrocarbons from different types of heavy feeds. Duringhydrocracking the hydrocarbons are cracked in the presence of hydrogen.Hydrocracking also facilitates the saturation of aromatics and olefins.

In one embodiment of the present invention the hydrotreatment comprisestreating the lignin with hydrogen gas or a hydrogen donor. The hydrogendonor may for example be formic acid or an alcohol or a combinationthereof. A non-limiting list of suitable alcohols is methanol (MeOH),ethanol (EtOH), propanol, iso-propanol (i-PrOH), glycerol, glycol,butanol, t-butanol (i-BuOH) or combinations thereof. The pressure in thereactor during the hydrotreatment may be 5 to 400 bar such as 50 bar orhigher, or 100 bar or higher, or 300 bar or lower, or 200 bar or lower,or 150 bar or lower. In one embodiment the hydrogen pressure is 20-200bar, such as 30-70 bar such as 40-60 bar. Since water is generatedduring the hydrogenation a large amount of energy is released. By usinga low hydrogen gas pressure this issue may be handled. Thehydrotreatment may be performed at a temperature of not more than 500°C., or not more than 400° C., preferably not more than 300° C., or notmore than 200° C., preferably at 100° C. or higher, or 150° C. orhigher. In one embodiment the hydrotreatment is done at a temperature of200 to 350° C.

In one embodiment the hydrotreatment is performed in the presence of acatalyst for HDS, HDO, and/or HDN. For example a transition metalcatalyst such as an Al, W, Ir, Re, Ni, Mo, Zr, Co, Ru, Rh, Pt or Pdbased catalyst. For example Raney nickel, nickel on carbon, Ni/Si,Ni/Fe, Nickel nanopowder, zeolite, amorphous silica-alumina, Pd/C, NiMoor CoMo or a combination thereof. In one embodiment the catalyst is aNiMo or a CoMo catalyst.

The components of the feedstock will be influenced differently whensubjected to the hydrotreatment process. The transformation of thelignin may be incremental and may require more than one pass through thehydrotreater before forming a fully deoxygenated product. On the firstpass lignin will partially be deoxygenated and depolymerized. Most ofthis material will follow the heavy fraction of depolymerized lignin(called green carrier liquid) back for a second pass through thehydrotreater. On the second pass through the hydrotreater it is morelikely that larger amounts of fully deoxygenated products form, i.e.liquid petroleum gas (LPG) and liquid fuel. By adjusting thedistillation parameter the middle distillates (diesel) can either formproduct or be recirculated for one more pass through the hydrotreater.Due to partial hydrocracking the recirculated fraction will eventuallyform LPG and light liquid fuel.

The hydrotreatment is performed until the amount of wanted products isobtained. For example the hydrotreatment may be done during at least 30minutes, or at least 1 hour, or at least 2 hours, or at least 4 hours.In one embodiment the hydrotreatment is done during 1-2 hours. FIG. 4discloses schematically the hydrotreatment products obtained whentreating different materials.

Distillation

The first product stream formed during hydrotreatment comprises lightcompounds and depolymerized lignin and the light compounds are in thenext step removed from the first product stream to form a second productstream comprising the heavy products and optionally also some residues.The removal of the light products may be done by distillation orevaporation under reduced or at atmospheric pressure.

FIG. 4 discloses a schematic view of the present invention where thedifferent distillation temperature intervals for the compounds, lightand heavy, are shown. The specific compounds and distillationtemperatures are only illustrative and should not be seen as limiting.

The partially deoxygenated heavy oil or green carrier liquid comprisesdepolymerized lignin which is a mixture of compounds. These compoundsmay have a mean boiling point of at least 165° C., preferably at least175° C., or at least 180° C. or preferably at least 200° C., or at least220° C. but may be less than 350° C., or less than 300, or less than250° C. The mixture may further comprise compounds that decompose beforereaching their boiling point at atmospheric pressure. In one embodimentthe mean boiling point is 200-350° C. The amount of said depolymerizedlignin in the green carrier liquid may be 70 wt % or more, or 80 wt % ormore, or 90 wt % or more, or 95 wt % or more, or 99 wt % or more. Thedepolymerized lignin may be phenol or phenol derivatives, polyphenols orpolyphenol derivatives such as alkylphenol, alkyl alkoxyphenol oralkoxyphenol or diphenols or a mixture thereof.

The depolymerized lignin in the green carrier liquid may also be definedby having a boiling point of at least 180° C., or at least 200° C., orat least 220° C., or at least 250° C., or at least 280° C., or at least300° C., or at least 330° C., or at least 350° C. The amount of saiddepolymerized lignin in the green carrier liquid may be 70 wt % or more,or 80 wt % or more, or 90 wt % or more, or 95 wt % or more, or 99 wt %or more. The green carrier liquid may comprise compounds that has aboiling point below each of these temperatures but then at low amountssuch as 10 wt % or less, or 5 wt % or less, or 2 wt % or less, or 0.5 wt% or less.

In one embodiment the amount of depolymerized lignin in the firstproduct stream that is used as green carrier liquid is at least 20%, orat least 40%, or at least 60%, or at least 70%, or at least 80%, or atleast 85% or at least 90% but less than 100%, or less than 95%.

The depolymerized lignin may also comprise hydrotreated oligomeric orpolymeric lignin herein called oligomeric hydrotreated lignin (OHL). Theoligomeric hydrotreated lignin will most likely have a reduced molecularweight in comparison with the lignin in the composition prior to thehydrotreatment however it might not have a boiling point due to that itdecomposes before reaching its boiling point. The hydrotreated lignin(OHL) is probably oligomeric but may be polymeric lignin. Thehydrotreated lignin may have a molecular weight (M_(w)) of 400 g/mol orhigher, or 600 g/mol or higher, or 800 g/mol or higher but preferablynot more than 1500 g/mol, or 1300 g/mol or lower, or 1000 g/mol orlower. The OHL may also be partly deoxygenated in comparison with thenon-hydrotreated lignin. The amount of OHL in the green carrier liquidmay be 0-50 wt % such as 1 wt % or higher, or 5 wt % or higher, or 10 wt% or higher, or 45 wt % or lower, or 35 wt % or lower, or 25 wt % orlower, or 15 wt % or lower. The amount of OHL in the green carrierliquid may be adjusted in order to optimize the system and the methodsuch as amount of hydrogen, flow, temperature and yield. By adjustingthe hydrogen pressure and temperature the amount of coke may be reduced.

Solvents

According to the present invention the composition comprisesdepolymerized lignin, preferably depolymerized Kraft lignin, which actsas a solvent and dissolves the lignin of the composition. Thedepolymerized lignin may be obtained by partly hydrotreating,hydrocracking or thermally cracking lignin.

The depolymerized lignin may be a mixture of phenol derivatives orpolyphenol derivatives such as phenol or polyphenols and an alkylphenol,alkyl alkoxyphenol or an alkoxyphenol. The phenol derivatives may havetwo or more hydroxyl groups. The polyphenols may be diphenols ortriphenols for example. In one embodiment the mixture comprises phenol,alkylphenol, alkyl alkxoyphenol and alkoxyphenol.

The phenol derivative according to the present invention has the generalstructure according to formula (1)

wherein each R1 to R6 may be individually selected from hydrogen,hydroxyl group, an alkyl group, an alkoxy group and alkyl alkoxy groupand wherein at least one of R1 to R6 is a hydroxyl group. In oneembodiment R6 is a hydroxyl group. In one embodiment the phenolderivative is a diol or a diphenol and preferably the hydroxyl groupsare in ortho position to each other. In one embodiment at least one ofR1 to R6 is an alkoxygroup such as a C1-C5 alkoxygroup. In oneembodiment an alkoxy group is in ortho position to the hydroxyl group.In one embodiment at least one of R1 to R6 is a C1-C10 alkyl group suchas a C1-C5 alkyl group. In one embodiment at least one of R1 to R6 is amethyl group. In one embodiment R6 is a hydroxyl group and at least oneof R1 or R5 is an alkoxy group, for example a methoxy group, and atleast one of R2-R4 is a C1-C5 alkyl group such as a methyl group orethyl group.

The polyphenol according to the present invention has the generalstructure according to formula (2a) or (2b)

wherein each R′ and R″ is individually a C1-C5 alkyl group, preferably aC2-C3 alkyl group and wherein each Ph₁ to Ph₃ is a phenol derivativeaccording to formula (1). The phenol derivatives (Ph) may be in ortho,meta or para position to each other. The phenol or polyphenolderivatives may be derived from lignin preferably Kraft lignin.

The mixture may comprise phenol derivatives and polyphenol derivativessuch as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and adiphenol. The weight proportion of phenol derivatives to polyphenolderivatives in the mixture may be from 1:100 to 100:1 (phenolderivative:polyphenol derivative).

Oxygenated products such as alcohols increase the hydrophilicity andthereby increases the amount of lignin that may be dissolved. In oneembodiment the mixture contains at least 50 wt % oxygenated compounds,or at least 70 wt % oxygenated compounds, or at least 90 wt % oxygenatedcompounds.

The depolymerized lignin in the composition may also comprisehydrotreated oligomeric or polymeric lignin herein called oligomerichydrotreated lignin (OHL). The oligomeric hydrotreated lignin may have areduced molecular weight in comparison with the lignin in the ligninfeed. The hydrotreated lignin (OHL) is probably oligomeric but may bepolymeric lignin and is preferably Kraft lignin. The hydrotreated ligninmay have a molecular weight (M_(w)) of 400 g/mol or higher, or 600 g/molor higher, or 800 g/mol or higher but preferably not more than 1500g/mol, or 1300 g/mol or lower, or 1000 g/mol or lower. The OHL may alsobe partly deoxygenated in comparison with the non-hydrotreated lignin.The amount of OHL in the depolymerized lignin may be 0-50 wt % such as 1wt % or higher, or 5 wt % or higher, or 10 wt % or higher, or 45 wt % orlower, or 35 wt % or lower, or 25 wt % or lower, or 15 wt % or lower ofthe total weight of the depolymerized lignin.

According to the present invention the composition may further comprisean added solvent. This solvent may be added to the first feed of ligninor, prior to or during the mixing of the second product stream with thesecond lignin feed. In one embodiment the composition does not compriseany added carrier liquid such a fossil fuel or oil or fatty acid orfatty acid ester.

The solvent may also be an organic solvent or a mixture of organicsolvents. In one embodiment the solvent is a mixture of an organicsolvent. The organic solvent may be but is not limited to oxygenatessuch as an ester, ether, alcohol, aldehyde, sulfoxide or ketone.Preferred solvents are C1-C10 alcohols, C1-C10 aldehydes, C2-C15ketones, C2-C10 ethers, and C2-C10 esters. A non-limiting list ofsolvents is methanol, ethanol, propanol, isopropanol, glycerol, phenol,alkylphenols or diols and butyl ether such as tert-butyl methyl ether;diethyl ether, diglyme, diisopropyl ether, dimethoxyethane, diethyleneglycol, diethyl ether, polyethylene glycol, 1,4-dioxane andtetrahydrofuran, methylated tetrahydrofuran, mesityl oxide, furfural,isophorone. Preferred C2-C10 esters are organic esters, aromatic ornon-aromatic esters, examples of esters are benzyl benzoate, variousacetates such as methyl acetate, ethyl acetate, cyclopentyl methyl etherand butyl acetate, various lactates such as ethyl lactates. Solventsthat are similar to or may be converted into fuel or petrol areinteresting when the composition is to be used for fuel preparation.Such solvents could be ketones, ethers or aldehydes. In one embodimentthe solvent is a C2-C15 ketone such as a C4-C12 ketone or a C6-C8ketone. In one embodiment the solvent is a C1-C10 aldehyde such as aC4-C9 aldehyde or C6-C8 aldehyde. In one embodiment the solvent is aC4-C10 ether. In one embodiment the solvent is a mixture of a C2-C15ketone and a C1-C10 aldehyde. In one embodiment the solvent is orcomprises mesityl oxide. In one embodiment the solvent is or comprisesacetone. In one embodiment the solvent is or comprises acetophenone. Inone embodiment the solvent is or comprises pentanone. In one embodimentthe solvent is or comprises ethyl isopropyl ketone. In one embodimentthe solvent is or comprises isophorone. In one embodiment the organicsolvent is or comprises an aromatic aldehyde or a mixture containing anaromatic aldehyde for example furfural. In one embodiment the solventcomprises furfural or furfuryl alcohol. In one embodiment the solvent isor comprises benzaldehyde. In one embodiment the solvent is or comprisesethyl acetate. In one embodiment the solvent is a C1-C10 alcohol or aC1-C10 diol. In one embodiment the solvent is or comprises ethanol. Inone embodiment the solvent is or comprises methanol. In one embodimentthe solvent is or comprises isopropanol. In one embodiment the solventis or comprises solketal. In one embodiment the solvent is or comprisesphenol. In one embodiment the solvent is a C2-C10 ester. In oneembodiment the solvent is or comprises tetrahydrofuran or methylatedtetrahydrofuran. In one embodiment the solvent is or comprises1,4-dioxane.

In one embodiment the solvent comprises a combination of C1-C10alcohols, C2-C10 ethers and C2-C10 esters. In one embodiment the solventcomprises two C1-C10 alcohols for example ethanol and glycerol, and inanother embodiment the solvent comprises propanol and glycerol. In oneembodiment the solvent comprises polyethylene glycol and a C1-C10alcohol. When the solvent is a mixture of an organic solvent and waterthe mixture may contain methanol and water, ethanol and water,isopropanol and water or ethyl acetate and water, preferably ethanol andwater, isopropanol and water and ethyl acetate and water.

In one embodiment the solvent is a mixture of a C2-C15 ketone such as aC4-C12 ketone or a C6-C8 ketone or a C1-C10 aldehyde such as a C4-C9aldehyde or C6-C8 aldehyde and an alcohol. In one embodiment the solventis a mixture of a C1-C10 alcohol such as a C3-C8 alcohol and analdehyde.

In one embodiment the amount of depolymerized lignin in the compositionis 1-99 weight % of the total weight of the composition. In oneembodiment the amount of depolymerized lignin is 10-90 weight %, or20-80 weight %. In one embodiment the amount of depolymerized lignin is75 weight % or less, or 70 weight % or less, or 65 weight % or less, or60 weight % or less, or 40 weight % or more, or 45 weight % or more, or50 weight % or more, or 55 weight % or more of the total weight of thecomposition.

In one embodiment the amount of added organic solvent in the compositionis 1-99 weight % of the total weight of the composition. In oneembodiment the amount of solvent is 10-60 weight %, or 20-50 weight %.In one embodiment the amount of organic solvent is 70 weight % or less,or 40 weight % or less, or 20 weight % or less, or 10 weight % or less,or 5 weight % or less, or 2 weight % or less of the total weight of thecomposition. In one embodiment the composition does not comprise anyadded organic solvent.

Pre-Treatments

The feed of lignin provided may be treated in a pre-treatment step priorto the step of providing the feed of lignin. The pre-treatment may beselected from membrane filtration, solvent extraction or acidificationand separation or a combination thereof. The purpose of thepre-treatment may be to remove unwanted products such as salts,catalysts or metal compounds which may damage the catalyst in thehydrotreatment step for example. If the feed is black liquor apre-treatment step may remove cooking chemicals which may be returned tothe pulping mill.

When using membrane filtration the cut-off of the membrane may be 200 to10,000 Da such as 200-5,000 Da or 500-1000 Da. The filtration may alsobe performed in several steps using membranes with different cut offs.For example the lignin feed may be filtrated using a filter having a cutoff of 10,000 Da and where after the permeate is diluted by addition ofwater or a suitable solvent and then filtrated using a membrane with acut-off of 200-1000 Da. The retentate is then used as the lignin feedaccording to the present invention. In another embodiment the ligninfeed may be filtrated using a filter having a cut off of 200-1000 Da andwhere after the permeate is diluted by addition of water or a suitablesolvent and then filtrated using a membrane with a cut-off of 200-1000Da. The retentate is then used as the lignin feed according to thepresent invention. The process may comprise recirculation of the liquidlignin composition and dilution of certain fractions containing ligninbefore subjecting to filtration, either in the incoming process flow toa filtration unit or in recirculated process liquid or both, at one ormore points downstream of a first filtration step. Recirculation ispreferably performed in a continuous loop, i.e. liquid is pumped fromone point to another point in the system upstream thereof. If desired,dilution is thereby performed by injecting solvent, e.g. water into therecirculation pipes by suitable pumping means. Dilution is believed tomake the removal of unwanted substances such as salts more efficient.

In its most general embodiment the process using dilution comprisessubjecting a liquid lignin containing composition, e.g. black liquor, toa first membrane filtration with a first filter cut-off adapted toseparate species in said liquid lignin containing composition infractions thereby providing a permeate and a retentate having respectivemolecular weight distributions defined by said cut-off; subjectingeither the retentate or the permeate from the first membrane filtrationto at least one further ultrafiltration step with a second filtercut-off different from said first filter cut-off to provide a retentate(concentrate) and a permeate having respective molecular weightdistributions defined by both the cut-off in the first filter and thecut-off in said second filter; recirculation of a fraction of the liquidlignin composition from a filter unit, suitably the retentate, back toinflowing liquid; wherein a dilution is performed on a desired lignincontaining fraction at some point downstream of the first filtrationunit; and collecting a desired lignin containing fraction, i.e. aretentate (concentrate) or a permeate from the further membranefiltration for further processing.

The lignin may also be precipitated by acidification followed byseparation such as decantation or filtration. The pre-treatment may be acombination of the above mentioned treatments and may comprise the stepsof membrane filtration, precipitation by acidification followed bymembrane filtration.

EXAMPLES Example 1

Solubility and Boiling Points:

Monomeric compounds attained after hydrotreating include alkylphenolics, aromatics, naphthalenes, catecholics, guaiacolics, alkanes,cyclic alkanes. These monomers in turn come from oligomeric lignin. Thesolubility of lignin in some of these compounds was investigated andcompound mixtures to show that lignin will be soluble in its ownhydrotreatment products. After hydrotreatment the products was separatedaccording to their boiling points (Table 1). The high boiling fractionis rich in oxygenates (phenolics) as these types of compounds have highboiling points while the fractions with a low boiling are largely fullydeoxygenated compounds and will be removed as product.

TABLE 1 Solubility of lignin in different solvents which are attainedfrom lignin hydrotreatment. Solvents bp [° C.] Solubility [wt %]Phenolics 4-ethylguaiacol 234 28 guaiacol 205 30 o-cresol 191 36 phenol182 35 Aromatics propylbenzene 159 Not soluble ethylbenzene 136 Notsoluble toluene 110 Not soluble Alkanes propylcyclohexane 155 Notsoluble nonane 151 Not soluble ethylcyclohexane 130 Not soluble octane125 Not soluble heptane 98 Not soluble cyclohexane 81 Not soluble

Mixtures of Oxygenated and Non-Oxygenated:

To reach an understanding of the proportions of oxygenated solventswhich can be used for carrier liquid for lignin, a quick study withdifferent proportions of one oxygenated (guaiacol) was performed and onenon-oxygenated solvent, propylbenzene (Table 2). To all samples 10 wt %of lignin was added. If the solvent composition contains less than 10%non-oxygenated solvents than it is quite easy to dissolved at least 10wt % lignin in the composition. To get mixtures with 10 wt % lignin intosolvent compositions containing 20 to 30% non-oxygenated solvent it ispreferable to heat the mixture above room temperature (70° C.).

TABLE 2 Solubility of lignin in solvent mixtures attained from ligninhydrotreatment. Amount of lignin solubilized by Solvent mixtureProportions solvent mixture Comments guaiacol 50:50 <10 propylbenzeneguaiacol 60:40 <10 propylbenzene guaiacol 70:30 10 Mostly dissolvedpropylbenzene at 70° C. guaiacol 80:20 10 Fully dissolved propylbenzeneat 70° C. guaiacol 90:10 >10 Fully dissolved propylbenzene at 25° C.

Batch Hydrotreating:

Several hydrotreating conditions have been attempted and the preliminaryresults show that hydrocarbons which have been fully deoxygenated may beproduced. Industrial grade NiMo catalyst was used under batch conditionsas a starting point. The first test under solvent free conditions (Table3, entry 1) showed that it was too mild hydrotreating conditions for toshort duration. Increasing the temperature to 350° C. and doubling thereaction time resulted in the recovery of a THF soluble fraction whichwas fully deoxygenated (Table 3, entry 2). The HSQC-NMR spectrum showsthat the original lignin is drastically transformed to yield ahydrocarbon product (FIG. 5).

TABLE 3 Hydrotreatment of lignin under various conditions. 10 min rampto temperature plateau from room temperature. Lignin H₂ Temp. Reactionconc. pressure plateau time Entry Solvent [wt %] [bar] [° C.] [h] 1 None100 50 300 1 2 None 100 50 350 2 3 guaiacol 50 50 350 4

Using guaiacol as a solvent was attempted with very nice results (Table3, entry 3). An amber-colored oil was obtained after the hydrotreatmentand according to the HSQC-NMR spectrum this oil is fully deoxygenated(FIG. 6). Obviously the spectrum mostly shows the sharp peaks fromproducts attained from guaiacol hydrotreatment. However, the spectrumdoes not contain signals from the oxygen containing groups found in theoriginal lignin and this result is very promising as many of theproducts formed when hydrotreating lignin is different types ofalkylphenols.

1. A composition comprising Kraft lignin having a weight average molecular weight (M_(w)) of at least 1,000 g/mol dissolved in depolymerized Kraft lignin.
 2. The composition according to claim 1 wherein the depolymerized lignin is a mixture comprising phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol.
 3. The composition according to claim 1 wherein the concentration of lignin is at least 1 wt %, or at least 3 wt %, or at least 5 wt %, or at least 10 wt %, or at least 15 wt %, or at least 25 wt %, or 40 wt % or less, or 35 wt % or less, or 30 wt % or less of the total weight of the composition.
 4. The composition according to claim 1 wherein no added carrier liquid is present.
 5. The composition according to claim 1 wherein the mixture comprises at least 50 wt % of oxygenated compounds.
 6. The composition according to claim 1 wherein the amount of lignin is 2-20 wt %; wherein the Kraft lignin has a weight average molecular weight (M_(w)) of higher than 1,500 g/mol but lower than 10,000 g/mol; wherein the amount of depolymerized Kraft lignin is 80-98 wt % and the depolymerized lignin comprises alkylphenols and alkoxy phenols.
 7. The composition according to claim 1 wherein the boiling point of the depolymerized lignin is at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C.
 8. The composition claim 1 wherein the composition is free of any particles having a diameter of 100 μm or more, or 50 μm or more, or 20 μm or more.
 9. The composition according to claim 1 wherein the depolymerized lignin is obtained by hydrotreatment or by hydrothermal treatment or hydrothermal cracking or solvolysis or any combination thereof.
 10. A method of preparing the composition according to claim 1 wherein the method comprises: a. providing a first feed of Kraft lignin having a weight average molecular weight (M_(w)) of at least 1,000 g/mol wherein the feed is a solution of Kraft lignin; b. hydrotreating the first feed forming a first product stream comprising light compounds and depolymerized lignin; c. removing the light compounds from the first product stream leaving a second product stream comprising the depolymerized lignin; d. providing a second feed of lignin; and e. mixing the depolymerized lignin with the second feed of lignin.
 11. The method according to claim 10 wherein the first feed of lignin is a mixture of the Kraft lignin and an organic solvent selected from an ester, ether, alcohol, aldehyde, sulfoxide or ketone.
 12. The method according to claim 10 wherein the hydrotreating step comprises treating the lignin with hydrogen gas or a hydrogen donor.
 13. The method according to claim 10 wherein the hydrotreating is performed together with a HDS, HDN or HDO catalyst such as a transition metal catalyst such as a Ni, Co, Mo, Zr, Ru, Pt or Pd based catalyst.
 14. The method according to claim 10 wherein the hydrotreating is performed at a temperature of not more than 500° C., or not more than 400° C., or not more than 300° C., or not more than 200° C., or at 100° C. or higher, or 150° C. or higher.
 15. The method according to claim 10 wherein the hydrotreating is performed at a pressure of 5 to 400 bar such as 50 bar or higher, or 100 bar or higher, or 300 bar or lower, or 200 bar or lower.
 16. The method according to claim 15 wherein the hydrotreating is performed at a hydrogen gas pressure of 100-150 bar.
 17. The method according to claim 10 wherein the first feed of lignin is a mixture of lignin and an alcohol such as phenol.
 18. The method according to claim 10 wherein the depolymerized lignin comprises compounds having a boiling point of at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C.
 19. The method according to claim 10 wherein the mixing of the second product stream and the second feed of lignin is done at a temperature of at least 50° C. or higher, or 70° C. or higher, or 90° C. or higher.
 20. The method according to claim 10 wherein the depolymerized lignin comprises a mixture comprising phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol.
 21. The method according to claim 10 wherein the feed of lignin provided in step a and d are treated in a pre-treatment step prior to step a and d respectively wherein the pre-treatment is selected from membrane filtration, solvent extraction or acidification and separation or a combination thereof.
 22. The method according to claim 10 wherein the amount of depolymerized lignin compounds having a boiling point of at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C., is at least 50 wt %, or at least 60 wt %, or at least 70 wt %, or at least 80 wt %, or at least 90 wt %, or at least 95 wt %.
 23. An intermediate composition comprising Kraft lignin having a weight average molecular weight (M_(w)) of 1,000 g/mol dissolved in depolymerized lignin.
 24. A The fuel obtained by the method according to claim
 10. 